The present invention relates to Hall-type transducing devices embodied in monolithic integrated circuits.
It is known to incorporate a Hall element along with other semiconductor components, such as an amplifier and switching circuit, into a single silicon-integrated circuit commonly referred to as a "chip," and to utilize the chip for the purpose of determining the presence of a magnetic field. Devices of the type are described in Anselmo et al. U.S. Pat. No. 3,816,766, issued June 11, 1974; in Avery U.S. Pat. No. 4,374,333, issued Feb. 15, 1983; and in Janssen U.S. Pat. No. 4,123,772, issued Oct. 31, 1978. It is also known that such intergrated circuits, as well as the components therein, have electrical characteristics that vary with changes in temperature. When these chips are used for the purpose of measuring the level of a particular strength field, care must be taken to assure that the ambient temperature is constant. Also, when these chips are used to detect the presence of a permanent magnet spaced a given distance therefrom the same constant temperature condition must be maintained as to the magnet also.
Transducing devices have employed actuating magnets capable of producing relatively strong fields in order to cope with the reduced strength of the magnets at relatively high temperatures. High temperature considerations, therefore, have determined the minimum magnet strength, and this in turn has determined the minimum physical size of the magnet: the larger the magnet, the stronger the field.
In the present invention, it is desired to employ relatively low energy magnet material, such as ferrite powder, in a plastic matrix as the actuating magnet. In the usual case, in order to obtain a sufficiently high energy output or field strength at high temperatures, the ferrite magnet must be large physically; hence, this material normally is not suitable for those applications in which space is limited.